Allow to modify the resource list dynamically

Created by: christopho

It is possible to create a map (other any file) dynamically, and to store it with the savegame, but it cannot be played now because it has to be declared in the resource list.

• sol.main.resource_exists(resource_type, id)
• sol.main.get_resource_description(resource_type, id)
• sol.main.add_resource(resource_type, id, description)
• sol.main.remove_resource(resource_type, id)